Offset printing is a widely used printing technique where the inked image is transferred (or “offset”) from a plate to a rubber blanket, then to the printing surface, e.g., paper. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a film of water, keeping the non-printing areas ink-free.
During the operation of the printing machine, ink regularly contaminates the non-printing areas, causing smears or smudges to appear on the printed surface, or in general interfere with the operation of the printing machine. In addition, pulp and dust from the paper used as the printing surface rises from the paper as the paper travels through the printing machine. This dust settles on the various parts of the printing machine, including the rollers, plates, and blankets, and contaminates these parts and interferes with the printing mechanism. In some applications, before they are fed to the printer, various pieces of paper are stacked on top of each other with a layer of spray powder, such as corn starch, separating them. The spray powder ensures that the pieces of paper do not stick together and are fed individually into the printing machine. Over time, the spray powder accumulates on the rollers, plates, and blankets and interferes with the printing mechanism.
Consequently, printing machines are cleaned regularly by applying a cleaning solution to the rollers, plates, and blankets to remove the ink and the grime from these parts. Traditionally, cleaning solutions have contained volatile organic compounds (VOCs). It is well-known that VOCs are not environmentally friendly. They are potential carcinogens, contribute to the depletion of the ozone layer, and may contribute to the green house effect that is responsible for global warming. As the result, governments have enacted restrictions on the use of VOCs in various industries, including the printing industry.
To comply with government regulations, various cleaning solutions having low VOC content have been marketed. These cleaning solutions are, for the most part, oil based. Oils have relatively low vapor pressures and are generally not considered to be volatile. However, oils are not satisfactory for use as printing machine cleaning agents. The oils in the cleaning solutions have a tendency to splatter. Once the oil has been used it accumulates at the bottom of the printing machine and then splatters on various parts, causing additional contamination. In addition, oils are difficult to remove and dispose.
Therefore, there is a need in the industry for a low VOC solvent that is compliant with governmental regulations, is economical to use, and cleans the printing machines efficiently and effectively.